I cut out four rib blanks and trued up two edges to create one square corner.

It's going to be necessary to bend these rib flanges on the (newly in service) 2' brake. In order to get the correct bend radius, I made some 2' long strips in order to build up the bend radius to the target 3T value. In this case, since I'm using .025 thick aluminum, the radius needs to be .075.

This new brake works really nice. Here are the bending guides on the leading edge of the tooling.

The bending stops were missing, so I fabricated these two from a piece of 1/4" rod.

Stops installed and adjustment screw set to achieve a 90 degree bend.

In preparation for bending the forward and aft flanges of the ribs, I did a couple test bends in a piece of scrap. The bend lines were drawn 1" apart, which yielded a part that is 1.068 long. So, since the ribs need to be 14.562 long, the bend lines should be drawn 14.494 apart.

I also made up a test part to check how the bend region results in additional length for the two legs.

In this case, this flange is 1.281 instead of the 1.260 you would get if you just subtracted off the 1" flange, which measured 1.047 (no picture, sorry). So, the total excess length is .068. Since the ribs need to be 14.563 long with a .625 flange at each end, just adding thes up would require a blank 15.813 long. However, this little test indicates we should reduce the length by .068 for each bend yielding a rib blank length of 15.677.